Mammoth Antarctic Iceberg A Disturbing Drifter

USHUAIA, Argentina — B-10A is hardly a sufficient name for the monster bobbing in the icy seas off Tierra del Fuego at the southern end of the world.

It is nearly the height of the Sears Tower, though four-fifths of it is underwater. It is 38 miles long and 13 miles wide, bigger than the Caribbean islands of Antigua, Aruba, Barbados and the Virgin Islands combined.

It is, simply, the biggest iceberg to drift from Antarctica in a long, long time. When a scientific vessel cruised around the monster recently, the trip--at 10 knots--took 12 hours.

"It's really big," said Andrea Barrio, a scientist at the Tourism Board of Tierra del Fuego's Antarctic Unit. "This is the biggest one anyone here remembers."

What separates B-10A from the other bergs that routinely break off Antarctica, however, is its location. The miniature continent is directly in the path that passenger cruise ships heading to Antarctica will use starting next month.

Worse yet, as it moves through sub-Antarctic waters, the iceberg is shedding cottage-size hunks of ice, known scientifically as "bergy bits" and piano-size pieces called "growlers."

A few football-field-size chunks have come crashing off too.

Are the strains of "Titanic" building in the South Atlantic? Not a chance, say scientists and tourism officials. Well, at least not much of one.

"There's no problem from the larger piece itself. The stuff that's hard to see are the smaller bergs calving off," said Jeff Andrews, the leading ice analyst at the National Ice Center in Washington, D.C.

Whether those could sink a ship "depends on where and how it struck," he said. "You could get rudder damage if you pushed backward into one." If a boat struck a berg head-on "it would cut the seam, cut through steel," he said. "It's that strong."

Largely because of technological advances, icebergs aren't the kind of problem they were for cruise ships in 1912, when the Titanic sank after striking a berg south of Newfoundland. More than 1,500 lives were lost.

Ships also are outfitted with sophisticated radar systems, and captains in iceberg-prone areas post 24-hour lookouts to keep an eye on the horizon for spots of "brilliance" associated with icebergs.

That has not completely eliminated accidents, however. A few years ago, Barrio remembers, a ship bound from Ushuaia to the Antarctic hit a small iceberg, which seriously dented its hull. The boat was never in danger of sinking but had to return to Ushuaia and then steam to Buenos Aires for repairs.

Fishing-ship captains working in the icy waters south of Tierra del Fuego say they have no desire to get anywhere near the huge new iceberg.

Asked if he had seen it or thought he would, Claudio Pertusi, the captain of the Spanish vessel Echizen Maro, moored at Ushuaia's windswept port, just shook his head vigorously.

"No, no, no, please," he said. "We hope not."

Scientists say the monster iceberg is in part the result of global warming, which has produced a growing frequency of large-scale ice breakoffs from the 1,000-foot-thick Antarctic ice shelf, which stretches away from the continent over the sea.

Increased use of fossil fuels around the globe since 1930 has raised temperatures in Antarctica and much of the world by 3.5 degrees Farenheit, scientists say. That has prompted an ever-faster rate of breakoffs from glaciers and ice shelves that, until recently, were "largely considered geographically permanent features," according to the National Ice Center.

A new study in the journal Science also suggests that the huge West Antarctic ice sheet may have been on its way toward total meltdown ever since the last Ice Age. The section of Antarctic ice that is deep enough to reach the ocean floor has been shrinking by about 400 feet a year for the past 7,600 years, the journal said.

The West Antarctic sheet eventually could disappear, the journal said, raising global sea levels by 15 to 20 feet, enough to submerge low-lying coastal areas and islands. The process, however, would take nearly 7,000 years.

B-10A, a tongue of the Thwaites Glacier that flows into the Amundsen Sea, broke away from Antarctica in 1985 but didn't begin moving away from the continent until 1992.

Since then, the National Ice Center has tracked it, watching as it split in half in 1995. The smaller piece--B-10B--drifted back toward the Antarctic ice pack, while B-10A headed north.

Larger bergs have broken from the Antarctic ice shelf, but this is the first of its size to make it far enough north to enter the shipping lanes south of Cape Horn, experts said.

Antarctic leopard seals, rarely seen as far north as Tierra del Fuego, have been following the berg, say wildlife officials in Ushuaia.

The iceberg, which is moving east at the rate of about eight miles a day, is now just east of the Drake Passage, near Elephant Island, a couple hundred miles from the southernmost point of Tierra del Fuego.

If the berg keeps its current route, it will head into the South Atlantic toward Africa, gradually melting in the warmer water over the course of several years, experts predict.

About three weeks ago, the National Ice Center, run by the Navy, Coast Guard and National Oceanic and Atmospheric Administration, issued a shipping warning on the berg, warning of the possibility of dangerous ice chunks in a radius of 165 miles around B-10A.

The warning is only advisory, and so far the 18 Antarctic cruise ships expected to head south from Ushuaia this season, starting in November, have not canceled their voyages or announced they will vary their routes, Barrio said.

Experts say they believe that the ships will ultimately change course to skirt the soup of icebergs, but such changes are voluntary.

"Safe navigation is up to the ship," Andrews said. "All we can do is get a warning out there and let them know what's there."